diff --git a/System.Application.SteamTools.Client.Desktop/Extensions/ViewModelExtensions.cs b/System.Application.SteamTools.Client.Desktop/Extensions/ViewModelExtensions.cs
index 6db13e749..a3c38610e 100644
--- a/System.Application.SteamTools.Client.Desktop/Extensions/ViewModelExtensions.cs
+++ b/System.Application.SteamTools.Client.Desktop/Extensions/ViewModelExtensions.cs
@@ -15,6 +15,11 @@ namespace System.Application
                 return disposable;
             }
 
+            if (vm.CompositeDisposable == null)
+            {
+                throw new ArgumentNullException(nameof(ViewModelBase.CompositeDisposable));
+            }
+
             vm.CompositeDisposable.Add(disposable);
             return disposable;
         }
diff --git a/System.Application.SteamTools.Client.Desktop/FileSystemDesktop.cs b/System.Application.SteamTools.Client.Desktop/FileSystemDesktop.cs
index cfab10cd3..c93aa9f76 100644
--- a/System.Application.SteamTools.Client.Desktop/FileSystemDesktop.cs
+++ b/System.Application.SteamTools.Client.Desktop/FileSystemDesktop.cs
@@ -1,5 +1,4 @@
-using System.Application.UI;
-using System.IO;
+using System.IO;
 
 namespace System.Application
 {